Tokyo, March 20 (IANS): Police in Japan on Thursday arrested a man on suspicion of making death threat calls to the US ambassador in Tokyo, media reported.

Mitsuyoshi Kamiya, 52, admitted to having made such calls thrice, threatening to bomb the embassy and a US military base in Okinawa prefecture between March 5 and 14, Xinhua reported citing Japan's Kyodo News.

US Ambassador to Japan Caroline Kennedy had received a number of death threats over the phone from a male English speaker, media reported.

According to the reports, the US embassy located in Tokyo's Minato Ward fielded calls in February from a man speaking English who said he was going to kill Kennedy.

Alfred Magleby, the US consul general in Naha in Okinawa prefecture, also received a number of death threats over the phone, reports said.

Kennedy is the daughter of former US president John F. Kennedy who himself was assassinated in 1963. She had arrived in Japan in 2013, and is the first woman to take up the top post in Japan, which has traditionally been held by high profile Americans.

She is known to be a staunch supporter of US President Barack Obama and had earlier attempted to oust Hillary Clinton in the Senate after Clinton became Obama's secretary of state.

The threat calls to Kennedy assumes significance in the wake of the knife attack on US Ambassador to South Korea Mark Lippert in Seoul earlier this month and sources believe that the threats calls to Kennedy may be part of a scheme to blackmail the envoy or the US embassy in Japan.

The US state department said in a statement that the government took "any threats to US diplomats seriously".

"We are working with the Japanese government to ensure that necessary security measures are in place, which is something we would do and continue to do around the world," State Department spokesperson Jennifer Psaki said.